Elastic fluid power plant control and protection



Aug. 3, 1937. E. s. THOMPSON ELASTIC FLUID POWER PLANT CONTROL AND PROTECTION- Filed July 22, 1936 Inverwtcr: EdwardSThorn son;

' His Attorney.

Patented Aug. 3, 1937 UNITED STATES PATENT OFFICE ELASTIC FLUID POWER PLANT CONTROL AND PROTECTION 7 Edward S. Thompson,

signor to General Electric Company,

tion of New York Schenectady, N. Y., as-

Application July 22, 1936, Serial No. 91,943

8 Claims.

The present invention relates to elastic fluid power plant control and protection, that is, to a system for controlling and protecting various elements of an elastic fluid power plant in response to certain conditions to which such elements are subjected. More specifically the invention relates to the control of elastic fluid generators and turbines in response to changes in elastic fluid conditions, although it is not limited thereto necessariiy. The invention is of particular significance in connection with forced circulation and flash boilers in which liquid is heated in heating elements and discharged into a drum or vessel at reduced pressure to be converted at least partly:

m tection whereby safe maximum load output may be maintained under varying conditions.

For a consideration of what I believe to be novel and my invention, attention is directed to 30 the following description and the claims appended thereto in connection with the accompanying drawing.

The single figure of the drawing illustrates a diagrammatic view of an elastic fluid power plant 5 embodying my invention.

The power plant shown in the present instance is a binary fluid plant consisting of a mercury fluid circuit and a steam circuit linked, in known manner, by a condenser boiler. The mercury 4 fluid circuit comprises a boiler Ill to which fuel is supplied for maintaining combustion by means including a valve II. The boiler has a heating element l2 which has a lower end receiving mercury liquid from a drum or vapor liquid sep- 45 arating device l3 by means of apump ll having an inlet l5 connected to the device It and a discharge It connected to the lower end of the heating element l2. The device It is fully disclosed in the application of Bigger and Hargrove Serial 50 No. 91,946 filed at the same date and assigned to the same assignee as the presentapplication. Liquid forced through the heating "element I2 is discharged at the upper end thereof and conducted by a conduit 11 to the liquid vapor sep- 55 arating device It. The liquid is recirculated from the device I! through the heating element l2 and the vapor is conducted from the device It through a conduit It to a mercury vapor turbine 19, whence the vapor is discharged into a condenser 20 to be condensed therein. The condensate is conducted from the condenser 20 by a conduit 2i and a pump 2la to the inlet l5 of the circulating pump it. The elements so far described form what is known as the mercury vapor circuit. The condenser 20 includes a cooling element 22, in the present instance shown diagrammatically as a coil which has an inlet connectedbya conduit 23 including a pump 24 to a source of cooling medium, in the present instance shown asla steam condenser 25. Water is forced from the condenset 25 by the pump 2| through the cooling element 22 in which the water is evaporated to be discharged to a steam turbine 26. The turbine exhausts into the condenser 25. The latter has an inlet 21 for conducting cooling medium to the condenser to eiIect condensation therein. The circuit including the coil 22, the turbine 26 and the condenser 25 forms the steam circuit. The condenser 2|! which serves to eilect condensation of the mercury vapor discharged from the turbine is and heating and evaporation'of the water flowing through the coil 22 is termed a condenser boiler. It forms the mercury and the steam circuit. V

As stated above, in forced circulation and flash type boilers it is desirable, particularly during high load conditions, to prevent evaporation of liquid within the heating element in order to permit maximum heat transfer to the heating element. Evaporation of liquid may be due to either one or a combination of two conditions. Evaporation is effected if at constant pressure of a liquid its temperature rises beyond a certain value, and evaporation is also eiiected if at constant temperature of a liquid its pressure is reduced below a certain value. The pressures and temperatures at such certain values are known as saturation pressures and temperatures respectively. For example, at a temperature of 1,126" F. the saturation pressure of mercury is 358 lbs.

At this pressure and temperaliquid is converted into vapor.

In order to prevent evaporation at 1,126" it is therefore desirable to subject the mercury to a slightly higher pressure, for instance,'to 380 lbs. per square inch. In other words, it is desirable to maintain a pressure diiferential of 22 lbs. per

link between the square inch. This pressure differential of- 22 lbs per square inch at the same time produces a temperature differential of 12 F. because at a presis 12 above 1,12 6.

380 lbs. per square inch absolute the mercury is in liquid form. Evaporation will if the pressure is reduced by at square inch absolute, or if the increased by 12 take place only least 22 lbs. per temperature is F., or if both values of pressure and temperature vary accordingly.

In accordance with my invention,'an elastic fluid power plant is provided with means for controlling the aforementioned pressure and temperature difierentials or, from another viewpoint, to prevent evaporation of the operating liquid, for instance mercury, as in the present case, within the heating element or elements of the boiler, In a preferred embodiment these means include a device responsive to pressure and temperature differentials of the operating liquid and means associated with the fuel supply for the boiler and in cooperative relation with the pressure and temperature differential responsive device to shut off the fuel supply whenever thetemperature or pressure difierential or both drop below fixed values. Thus, the supply of fuel to the boiler to maintain combustion therein is controlled in response to pressure and temperature conditions of the operating liquid discharged from the heating elements. These pressure and temperature conditions depend upon several variables and in a many cases it is desirable to control the fuel supto shut down the turbine in response to certain changes ply in response to changes of these and other variables. One of these variables is the speed of a prime mover, for instance, a turbine receiving fluid from the boiler. As the speed'rises to a certain value oremergency speed, it is desirable and simultaneously the boiler. Another of these variables is the pressure of the elastic fluid conducted to the turbine. Whenever this pressure rises beyond a certain maximum value, it is desirable to shut oi). the fuel supply to the boiler.

Referring now more specifically to the arrangement shown in the drawing, the fuel supply valve during normal operating condition is held in open position by means of an electromagnet having a core 3|) connected to an arm 3| of the valve and a coil 32 forming a part of an electric circuit with one end of the coil 32 a conductor 33. and a switch 34 to a source of electric energy 35 and the other end of the 0011 connected by another conductor 36 to the source 35. v The electric. circuit includes a plurality ,of contacts or switches which are opened and closed of operating conditions. A pair of contacts, in the present instance forming a part of a mercury switch 31, is controlled by a temperature pressure diiferential responsive device which has been indicated diagrammatically as including a pressure-responsive element 38 in the form of a Bourdon tube and a temperature-responsive element 39 also in the form of a Bourdon tube. The pressure-responsive element 38 has an open lower end portion communicating with the discharge conduit H of the heating element l2. The free ends of the Bourdon tubes are connected by a floating lever '4ll which has an. intermediate point pivotally' latter movement of the left-hand endof the floating without affecting the connected by lever 40, thus moving the switch towards opening position. Similarly, a decrease in pressure at constant temperature causes upward move ment of the right-hand end of the lever 40 and turning of the switch 31 towards opening position. A decrease'in pressure and 2. corresponding simultaneous decrease in temperature causes counterclockwise turning of the lever 40 about its intermediate pivotal connection 'to the switch latter. The temperatureresponsive element 39, has a sealed end portion disposed within the conduit I1. The Bourdon tube 39 contains the same liquid as the boiler, in the present instance mercury. If the pressure of the fluid drops a certain value, which heretofore I termed a pressure difierential. for instance 22 lbs. per square inch, the switch 31 is opened, assuming that the temperature remained constant. Similarly, if under constant pressure conditions thetemperature drops a certain value, heretofore termed temperature differential, for instance 12 F. as in the above example, the electric circuit is also opened. Opening of the circuit causes closing of the fuel supply valve II by the action of a spring 4|, biasing the valve arm 3| towards-closing position. In the preferred embodiment, as shown, the temperature pressure difierenti-al responsive device (31 to 40) is connected to the discharge conduit ll of the heating element l2, that is, ahead of the drum H. A pair of contacts 42 connected in series with the switch 31 is controlled in response to changes of the pressure of the fluid conducted to the turbine. The contacts 42 are normally closd by a contact-making member 43 secured to a stem 44 which is connectedto a diaphragm 45 of a pres- The lower side of the sure-responsive device 46. diaphragm 45 is subjected to-the fluid pressure in the turbine inlet conduit l8 and the upper side of the diaphragm 45 is biased downward by a spring 41. contact-making member 43 is moved upward against the force of the spring 41 to open the circuit as the fluid pressure in the turbine inlet conduit I8 reaches a certain maximum value. Opening of the contacts 42, like opening of the switch 31, interrupts the circuit for the coil 32 and thus causes closing of the fuel supply valve I by the action of the spring 4|.

As pointed out above, it is desirable to shut down the boiler, that is, to close the fuel supply valve M if the turbine speed reaches a certain emergency value. In the usual power plant arrangement, turbines are provided with emergency speed governors and valves actuated by the speed governors for shutting down the turbine in response to a certain maximum speed. In the present instance the power plant includes two turbines l9 and 26 and both turbines are provided with means for effecting closing of the fuel supply valve I in response to certain speed conditions; The turbine l9 has an emergency speed governor 48 driven from the turbine shaft and provided with .a switch operating member 49. The electric circuit includes contacts or switch members 50 and 5|, the latter being normally biased towards the contact 50 by the action of a compression spring 52. As the speed of the turbin'e rises and reaches emergency speed, the governor flyweights by the action oi centrifugal force moveoutward'and thus cause downward turbine 26 is provided'with a centrifugal type .ernergency speed. governor 53 driven from the The arrangement is such that the,

steam turbine reaches a certain maximum value, the centrifugal weights of the governor are forced outward and in a certain position effect opening of the contacts 55, 55, the contact 55 being forced downward against the action of the compression spring 51. Opening of either contacts 55, 5| or 55, 55 interrupts the electric circuit, deenergizing the coil 32 and resulting in closing of the fuel supply valve ll of the boiler.

An important problem in elastic fluid power plants is the sealing of certain elements normally subjected to pressures below atmosphere to prevent leakage of air into such element. One such element is the elastic fluid turbine. The sealing of the turbine shaft against the casing is especial- 1y important in mercury power plants, that is, where turbines are operated by mercury vapor because air leaking into the turbine may be conducted therefrom to the boiler and cause oxidation therein of the boiler walls and the mercury. The leakage of air into the turbine may be overcome by the provision of sealing means forming chambers around .the shaft to which an inert or non-oxidizing gas, for instance nitrogen, is supplied at a pressure slightly above atmosphere. In the present instance the turbine l5 has sealing chambers 55 and 59 to which nitrogen or other:

gas is supplied at a pressure slightly above atmosphere by means including a conduit 55 having branches 5| and 52 connected to the chambers 55 and 55 respectively. The conduit 55 receives gas from a suitable source, not shown, and includes a valve 53 which is closed during operation and opened when the turbine is shut down. In accordance with my invention the valve 53 is normally held in closed position by an electromagnet having a core 55 and an energizing coil 55 connected in series with the aforementioned contacts.

' If one of the contacts is opened, the electric circuit is interrupted and consequently the coil 55 is deenergized, resulting in opening of the valve 53 by the action of a'spring 55.

Thus, with the arrangement described above, the fuel supply valve II is closed and the nitrogen supply valve 53 is opened in response to first, a certain increase in temperature of the fluid discharged from the heating element I! to the drum l3; second, a certain decrease in pressure of the fluid discharged from the heating element l2; third, a combination of tin: causes mentioned under number one and two; fourth, a certain increase in pressure of the fluid conducted to the elastic fluid turbine l3; and fifth, a certain increase in speed of either turbine is or turbine 25.

In many cases there is no objection to the evaporation of fluid within the heating element or elements during light load conditions. To meet such a situation, means are provided for rendering the temperature pressure differential responsive device (35 to 55) inoperative or rather ineffective as the load on the turbine reaches a certain low value, for instance one-third load. The means for accomplishing this in the present example is a load-responsive device in the form of a pressure-responsive device having a casing 51 divided into two halves by a diaphragm 55.

The lower half, that is, the space below the diaphragm communicates by a pipe 55 with the high pressure end, preferably the flrst stage shell, of the turbine l5.

Thus, the diaphragm 55 is the spring 1| until velocity of fluid which normally would cause the subjected to the first stage shell pressure of the turbine l3, which pressure is substantially proportional to the load output of the turbine. The diaphragm carries a stem 15 and is biased in downward direction by a spring 1| surrounding the stem. A contact-making member 12 is secured to the upper end of the stem and arranged in cooperative relation with two contacts 13 connected by conductors 14 and 15 to the terminals of the temperature pressure differential responsive device (38 to 45) so as to bridge the switch 31 whenever the contacts 13 are closed. A decrease in load of the turbine is causes a decrease in the first stage shell pressure whereby the diaphra'gm 55 is forced downward by the action of finally a certain pressure corresponding to. a certain low load is reached when the contact-making member 12 bridges the contacts 13 and thus short-circuits the switch 51. When this occurs, opening of the switch 31 no longer interrupts the electric. circuit, the temperature pressure diiferential responsive device then being ineffective or short-circuited and vapor may be produced within the heating coil l3.

Another important feature of my invention is the provision of means for. controlling the circulation of fluid through the heating coil II in response to fluid conditions in the discharge conduit l1. It is desirable to increase the amount of fluid forced through the coil, that is, to increase the within the coil, in response to increasing temperature at constant pressure and in response to decreasing pressure at constant temperature, that is, in response to a condition fluid to evapo rate within the heating coil. To this end the circulating pump H for forcing liquid into the heating coil I2 is driven by a variable speed motor 15, in the present instance shown as a direct current motor having a fleld 11 with a resistance 15 connected in series with the field 11. The resistance 15 is normally shortircuited by means of a relay 1!] having a coil 55 connected in series with the aforementioned electric circuit including the switch 31 operated by the pressure-temperature diflerential responsive device. when the switch 31 opens, the electric circuit is interrupted and the coil deenergized, causing opening of the relay by the action of a spring 5| whereby the flow of current through the field coil 1.1 is reduced due to the increase in resistance and con-- sequently the speed of the motor 15 is increased, causing an increase in speed of the pump it with the resulting increased flow of liquid through the heating coil l2.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An elastic fluid power plant including the combination of a boiler having an element for receiving and heating liquid, a conduit including temperature difl'erential responsive device having elements subject to the pressure and the temperature of the liquid discharged from the heating element, fuel supply means for the boiler, and means including said device for controlling the fuel supply means.

3. An elastic fluid power plant including the combination of a-boiler having a heating element, means for conducting liquid to the heating element, a drum for receiving liquid from the heating element and conuerting liquid into vapor, a conduit including a valve for conducting fuel to the boiler to maintain combustion therein, and a device responsive to pressure and temperature dlfl'erentials of the fluid discharged from the heating element for closing said valve when the pressure and temperature differentials of the fluid reach certain minimum values.

4. An elastic fluid power plant including the combination of a boiler, an elastic fluid turbine having an inlet conduit connected to the boiler, a conduit including avalve for conducting fuel to the boiler, means including an electromagnet having an energizing coil and an electric circuit including a pair of normally closed contacts for energizing the coil to maintain the valve open, and a device responsive to the pressure of the elastic fluid conducted to the turbine for opening said contacts when the pressure of the fluid rises beyond a certain value.

5. An elastic fluid power plant including the combination of a boiler having a heating element for receiving and heating liquid, a liquid vapor separating drum connected to. the element for receiving heated liquid therefrom and converting it into vapor, a conduit including a valve for conducting iuel to the boiler, an electric circuit including an electromagnet normally to maintain the valve open, means including a pair of contacts in said circuit and a device responsive to pressure and temperature differentials oi the liquid discharged from .the heating element to eflect opening of said contacts and interrupting oi the circuit when the pressure and temperature diflerentials of the liquid discharged from the heating element drop below a certain minimum value, and means responsiveto load output of the boiler for rendering said device inoperative when the load output drops below a certain value.

6,.An elastic fluid power plant including the combination or a p a pump connected to boiler having a heating element, means for conducting liquid to the heating element, a liquid vapor separating drum for receiving heated liquid from said element and converting it into vapor, an elastic fluid turbine having an inlet connected to the drum, a conduit including a valve to maintain combustion therein, means biasing the valve towards closing position, other means including an electric circuit with a plurality of pairs 01 contacts normally to hold the valve in open position, means including one pair of contactsto open the circuit when the pressure and temperature difl'erentials oi the fluid discharged from the heating elements reach certain minimum values, means including another pair of contacts for opening said circuits when the pressure of the fluid conducted to the turbine rises beyond a certain maximum value, means including another pair of contacts for opening said circuit when the certain value, and means for sealing the turbine shaft against the casing'when the turbine operation is interrupted comprising sealing chambers associated with the turbine shaft, a conduit including a valve for conducting gas to said chambers and means including an electromagnet having a coil connected in series with said circuit for conducting fuel to the boiler speed of the turbine rises beyond a normally to maintain said valve closed and a spring to effect openingoi said valve when said circuit is interrupted.

7. An elastic fluid power plant including the combination of a boiler having an element for receiving a heating liquid, means for forcing liquid through the element, means for receiving heated liquid from the element. and means for controlling the flow oi liquid through the element in response to pressure temperature difl'erential conditions of the heated liquid discharged from the element.

8. An elastic fluid power plant including the combination of a heating element having an inlet conduit and a discharge conduit, means including the inlet conduit for forcing liquid through the heatlng element, a motor for driving the pump, and means including a pres-- sure temperature difl'erential responsive device connected to the discharge conduit for controlling the speed of the motor.

EDWARD S. THOMPSON.

- CoNraonANn .zclailtner filed March 22., LHjerelg disclaims claim 4 of Gazette 1.9-, 1988.]

mompmgscheimctcg,"118i.1 Y; Emrs'rro FLuInPow'Ea Paorpcmou. a 1938, byth'e assignee,- General Electric Company.

tent dated August a, 1937. vnit;-

said Letters Patent.

temperature difl'erential responsive device having elements subject to the pressure and the temperature of the liquid discharged from the heating element, fuel supply means for the boiler, and means including said device for controlling the fuel supply means.

3. An elastic fluid power plant including the combination of a-boiler having a heating element, means for conducting liquid to the heating element, a drum for receiving liquid from the heating element and conuerting liquid into vapor, a conduit including a valve for conducting fuel to the boiler to maintain combustion therein, and a device responsive to pressure and temperature dlfl'erentials of the fluid discharged from the heating element for closing said valve when the pressure and temperature differentials of the fluid reach certain minimum values.

4. An elastic fluid power plant including the combination of a boiler, an elastic fluid turbine having an inlet conduit connected to the boiler, a conduit including avalve for conducting fuel to the boiler, means including an electromagnet having an energizing coil and an electric circuit including a pair of normally closed contacts for energizing the coil to maintain the valve open, and a device responsive to the pressure of the elastic fluid conducted to the turbine for opening said contacts when the pressure of the fluid rises beyond a certain value.

5. An elastic fluid power plant including the combination of a boiler having a heating element for receiving and heating liquid, a liquid vapor separating drum connected to. the element for receiving heated liquid therefrom and converting it into vapor, a conduit including a valve for conducting iuel to the boiler, an electric circuit including an electromagnet normally to maintain the valve open, means including a pair of contacts in said circuit and a device responsive to pressure and temperature differentials oi the liquid discharged from .the heating element to eflect opening of said contacts and interrupting oi the circuit when the pressure and temperature diflerentials of the liquid discharged from the heating element drop below a certain minimum value, and means responsiveto load output of the boiler for rendering said device inoperative when the load output drops below a certain value.

6,.An elastic fluid power plant including the combination or a p a pump connected to boiler having a heating element, means for conducting liquid to the heating element, a liquid vapor separating drum for receiving heated liquid from said element and converting it into vapor, an elastic fluid turbine having an inlet connected to the drum, a conduit including a valve to maintain combustion therein, means biasing the valve towards closing position, other means including an electric circuit with a plurality of pairs 01 contacts normally to hold the valve in open position, means including one pair of contactsto open the circuit when the pressure and temperature difl'erentials oi the fluid discharged from the heating elements reach certain minimum values, means including another pair of contacts for opening said circuits when the pressure of the fluid conducted to the turbine rises beyond a certain maximum value, means including another pair of contacts for opening said circuit when the certain value, and means for sealing the turbine shaft against the casing'when the turbine operation is interrupted comprising sealing chambers associated with the turbine shaft, a conduit including a valve for conducting gas to said chambers and means including an electromagnet having a coil connected in series with said circuit for conducting fuel to the boiler speed of the turbine rises beyond a normally to maintain said valve closed and a spring to effect openingoi said valve when said circuit is interrupted.

7. An elastic fluid power plant including the combination of a boiler having an element for receiving a heating liquid, means for forcing liquid through the element, means for receiving heated liquid from the element. and means for controlling the flow oi liquid through the element in response to pressure temperature difl'erential conditions of the heated liquid discharged from the element.

8. An elastic fluid power plant including the combination of a heating element having an inlet conduit and a discharge conduit, means including the inlet conduit for forcing liquid through the heatlng element, a motor for driving the pump, and means including a pres-- sure temperature difl'erential responsive device connected to the discharge conduit for controlling the speed of the motor.

EDWARD S. THOMPSON.

- CoNraonANn .zclailtner filed March 22., LHjerelg disclaims claim 4 of Gazette 1.9-, 1988.]

mompmgscheimctcg,"118i.1 Y; Emrs'rro FLuInPow'Ea Paorpcmou. a 1938, byth'e assignee,- General Electric Company.

tent dated August a, 1937. vnit;-

said Letters Patent. 

